Background of the Invention
Each eyeglass lens typically has a peripheral beveled edge which seats in a corresponding groove in the eyeglass frame. Typically, the frame is sized to fit the wearer and the lenses must therefore be appropriately sized to fit the frame. Customarily, a right lens and a left lens are required, with the lenses not normally being interchangable. It has been common practice for the optician to stock a supply of lens blanks for the frames, the blanks having the required optical properties and being capable of being cut to the proper size.
Conventional glass lenses are cut to size and beveled with a relatively slowly rotating diamond wheel. Plastic lenses have increased in popularity more recently and conventional diamond grinding techniques are too slow. Router techniques have been used with plastic lenses in view of the highspeed cutting available but pattern warpage has been a problem.
The number and styles of eyeglass frames has increased tremendously and each style typically requires a special lens configuration. It is impractical for the optician to stock a supply of sized blanks for each style of frame, particularly when the necessary optical properties are considered. Furthermore, because of the numerous frame styles, the optician must be able to rapidly shift his shaper and edger from one frame style to another. Typically, each framemaker provides the optician with a pattern or patterns which are used to cut the lenses to fit the frame. Generally, there is one pattern per frame style so the edger and shaper must be able to appropriately cut the lens to the proper size for the given frame.
The high speed rotary cutters used in conventional router techniques generate much dust which must be evacuated to prevent damage to the machine. Furthermore, because of the high speeds employed, it is important that the edger and shaper have appropriate safety devices to prevent the operator from being injured. Conventional diamond grinding machines, on the other hand, generate large quantities of wet waste.
The disclosed invention is a plastic lens shaper and finisher employing router techniques in a manner which permits high speed cutting and finishing of the lenses in a safe way while successfully avoiding the problem of pattern warpage. The invention furthermore can be equipped with digital control systems to eliminate the need for individual physical patterns. The invention utilizes relatively low pressure pneumatic drive systems to control the movement between the shaping and finishing operations so that speed is maximized while pressure on the blank being cut is minimized. Lastly, the disclosed invention is particularly suited for an environment wherein long production runs are not possible and rapid interchangability from one frame style to another is required.
Objects and Summary of the Invention
The primary object of the disclosed invention is to provide a plastic lens shaper and finisher which minimizes the force which is applied to the pattern during the cutting operation by mounting the head of the edger for movement in the same plane relative to the carriage assembly which carries the cutter motor.
A further object of the disclosed invention is to provide a plastic lens shaper and finisher wherein the pattern engaging roller assembly is mounted horizontally parallel to the base of the device opposite to the lens drive assembly and wherein the roller rotates on a plane common with the router.
Another object of the disclosed invention is to provide a plastic lens shaper and finisher having pneumatic drive systems provided by cylinder and piston assemblies for the carriage and the head such that one assembly causes rapid movement whereas the other acts as a damping device to minimize the shock of engagement between the router and the raw blank.
In summary, the disclosed invention is a plastic lens shaper and finisher having a metallic bed to which a first frame is mounted for reciprocating motion along a first axis. A router assembly is mounted to the first frame and rotates on a second axis which is parallel to the first. A second frame is mounted to the bed for reciprocating motion along a third axis transverse to the first and second axes and carries a chuck for holding a plastic blank to be shaped. The second frame also carries a pattern holding assembly which rotates in combination with the blank by means of a common motor. A pneumatic drive system is connected to the first frame for moving the first frame between a shape position and a finish position. A similar pneumatic drive system is mounted to the second frame for moving the second frame so that the blank is cut by the router into the appropriate shape and size.
These and other objects and advantages of the invention will be readily apparent in view of the following description and drawings of the above described invention.
Description of the Drawings
The above and other objects and advantages and novel features of the present invention will become apparent from the following detailed description of the preferred embodiment of the invention illustrated in the accompanying drawings, wherein:
FIG. 1 is a perspective view of the plastic lens shaper and finisher of the invention mounted in its case;
FIG. 2 is a rear elevational view of FIG. 1;
FIG. 3 is a top plan view of the invention with the case removed to permit viewing of the innerworkings;
FIG. 4 is a fragmentary cross-sectional view taken along the section 4--4 of FIG. 3 and viewed in the direction of the arrows;
FIG. 5 is a fragmentary cross-sectional view taken along the section 5--5 of FIG. 3 and viewed in the direction of the arrows;
FIG. 6 is a fragmentary elevational view partially in section taken along the section 6--6 of FIG. 3 and viewed in the direction of the arrows;
FIG. 7 is a fragmentary side elevational view partially in section;
FIG. 8 is a cross-sectional view taken along the section 8--8 of FIG. 3;
FIG. 9 is a top plan view illustrating the device in the finish position; and,
FIG. 10 is a schematic view illustrating the control system of the invention.
Description of the Invention
Plastic lens shaper and finisher P, as best shown in FIG. 1, is particularly intended for the shaping and finishing of plastic lenses although use on other parts is not unanticipated. As used herein, plastic eyeglass lenses include lenses manufactured from CR 39, acrylic and polycarbonate compositions. Naturally, the continuing development of eyeglass technology may result in additional compositions being found suitable for use and the present disclosure is not intended to be limited to the three listed compositions, they being merely illustrative.
Plastic lens shaper and finisher P has an enclosure comprised of bottom member 10 and cover member 12 hingedly connected thereto. Preferably, catch 14 secures cover member 12 to bottom member 10 and prevents unintended opening thereof. Cover member 12 has a clear window 16 mounted thereto by hinges 18, for reasons to be explained later. As illustrated in phantom lines in FIG. 1, electric light 20 is mounted to cover member 12 proximate window 16 to illuminate the device during operation. Also disclosed in FIG. 1 is mercury switch 22 secured to window 16 and pivotal therewith for safety reasons which will be further discussed.
FIG. 1 furthermore discloses air pressure gauges 24, 26 and 28 used in regulating the pneumatic control systems which will be further explained. Also disclosed in FIG. 1 are control switches 30, 32, 34, 46, 38 and 40 which are used in the operation of the device. It can be noted that cover member 12 includes a shelf 42 having an upstanding peripheral wall 44 for holding job trays of finished and uncut blanks.
FIG. 2 discloses the filter assembly 46 as well as connection 48 to the air supply line (not shown). Also illustrated are plug connections 50 and 52 providing control and operating power for shaper and finisher P. Regulators 54, 56 and 58 are also illustrated in FIG. 2, each regulator being associated with one of gauges 24, 26 and 28 for regulating the operating pressure outputted therefrom.
As best shown in FIG. 4, member 10 is a plastic shell which encloses metallic bed 60. Bed 60 has an upper planar surface 62. Sound damping insulation 64 extends along the side walls of member 10. While member 10 is disclosed as a plastic shell, those skilled in the art will appreciate that it can be constructed of other materials. Likewise, cover member 12 is also preferably a plastic shell.
As best shown in FIG. 6, spaced parallel support blocks 66 and 68 are secured to bed 60. Rods 70 and 72, as best shown in FIGS. 3 and 6, extend between blocks 66 and 68 in spaced parallel relation and are uniformly spaced above surface 62. Supports 74 and 76 are disposed in spaced parallel relation and are slidably mounted to rods 70 and 72 for movement therealong. First frame 78 is secured to supports 74 and 76 and is movable therewith. Mounts 80 and 82, as best shown in FIG. 3, are secured to bed 60 on either side of frame 78. Pneumatic cylinder 84 is secured to mount 80 and piston rod 86 thereof engages and bears upon link 92 secured to and depending from frame 78.
Pneumatic cylinder 94 is secured to mount 82 and piston rod 96 extends therefrom and through link 98 which is secured to and depends from frame 78. Unlike piston rod 86, piston rod 96 has a nut 100 which permits the rod 96 to slide freely through aperture 101, toward the right as viewed in FIG. 3, without causing corresponding movement of frame 78. The nut 100 does, however, engage link 98 upon the piston rod 96 being retracted, or moved toward the left as viewed in FIG. 3, for causing corresponding movement of the frame 78. It can be noted that the cylinder 84 is substantially smaller than the cylinder 94, as is the corresponding piston rod 86 to rod 96. The piston 86 moves rapidly relative to piston 96 for thereby causing associated rapid movement of frame 78. The cylinder 94 is large relative to cylinder 84 and thereby provides a damping effect during movement of the frame 78 by the piston rod 86. In other words, the piston rod 96 limits the absolute movement of the frame 78 and acts as a shock absorber as the frame 78 is moved by the piston rod 86.
As best shown in FIG. 3, electric motor 102 having a high speed rotating shaft 104 is secured to frame 78 by mounts 105. Router head 106 is secured by nut 108 to shaft 104 and carries cutter blades 110. Preferably, each of the blades 110 has a straight portion 112 and a V-portion 114 which bevels the lens blank, as will be further explained. It should be appreciated that the shaft 104 rotates on an axis which is parallel to the axis on which the frame 78 moves.
Bracket 116, as shown in FIGS. 3 and 6, is secured to frame 78 and is movable therewith. Rod handle 118 extends therefrom and terminates in handle 120, as shown in FIG. 1. Rods 122 and 124 extend from bracket 116 oppositely to rod handle 118 and are received within apertures in block 126. Coil springs 128 and 130 are mounted to the rods 122 and 124, respectively, and adjustment knob 132 extends from block 126, for reasons to be explained later. Catch rod 134 extends from bracket 116 parallel to rods 122 and 124, as best shown in FIG. 3. Latch 136 extends downwardly from window 16 and has an aperture 138 through which rod 134 passes. In this way, shifting of frame 78 towards the left, as viewed in FIGS. 3 and 6, will cause the rod 134 to pass through the aperture 138 and therefore prevent opening of window 16.
FIG. 5 discloses opening 140 in bed 60. Plastic shroud 142 is secured in opening 140 and extends upwardly therefrom and terminates proximate router 106. A vacuum assembly (not illustrated) is operatively connected with shroud 142 for evacuating dust and the like generated by router 106 during operation thereof. In this way, the dust and other particles do not fill the edger and shaper P and block viewing of the components thereof.
As best shown in FIG. 7, support blocks 144 and 146 are mounted in spaced parallel relation to bed 60. Rods 148 and 150, as best shown in FIGS. 7 and 4, extend between blocks 144 and 146 in spaced parallel relation and are a uniform distance from surface 62, the distance being equal to that of rods 70 and 72 from bed 60. The rods 148 and 150 extend in a direction generally transverse to the direction in which the rods 70 and 72 extend. Supports 152 and 154 are disposed in spaced parallel relation and are slidably mounted to rods 148 and 150 for movement therealong. Second frame 156 is mounted to supports 152 and 154 and is movable therewith, as will be further explained.
As best shown in FIGS. 3 and 4, links 158 and 160 are secured to and extend outwardly from frame 156 along opposite sides thereof. Support blocks 162 and 164 are secured to bed 60 proximate links 158 and 160, respectively. Pneumatic cylinder 166 is secured to support block 162 and the piston rod 168 thereof is engaged with and bears upon link 158 in a manner similar to the engagement of rod 86 to link 92. Pneumatic cylinder 174 is likewise secured to its support block 164. The piston rod 176 thereof extends through an aperture 177 in link 160 and has lock nuts 178 mounted thereto. As with the piston rod 96, rod 176 may freely slide relative to the link 160 in a first direction but, in the opposite direction thereto, the nut 178 engages the link 160 and causes movement thereof. As with the cylinder and piston assemblies 84, 86 and 94, 96 respectively, of first frame 78, the cylinder and piston assemblies 166, 168 and 174, 176 move the second frame 156 along an axis which is generally transverse to the axis on which the first frame 78 moves. As before, the cylinder 166 is a high speed movement cylinder whereas the cylinder 174 acts as a damping cylinder, to prevent shocking impact with router 106.
Motor 180 is secured to second frame 156 and extends generally transverse to the axis on which the router 106 rotates. Motor 180 is connected to transmission 182 from which shafts 184 and 186 extend in coaxial alignment generally transverse to the axis on which the second frame 156 moves. Shaft 184 has a coupling 187 from which shaft 188 extends in coaxial alignment. First blank holding member 190 is mounted for coaxial rotation which shaft 188 and has a pad 192 which engages plastic blank 194.
It can be noted in FIG. 3 that second frame 156 is generally L-shaped in plan. Support members 196 and 198 are secured to second frame 156 in spaced parallel relation. Wall members 200 and 202 extend therebetween and are likewise secured to second frame 156. Cylinder 204 is secured to support member 198 by lock nut 206. The piston rod 208 thereof extends through aperture 210 of support member 196 and has a cover 212 at the distal end thereof.
Arm 214 is secured to piston rod 208 and includes an extension member 216 which extends through a longitudinally extending slot in wall member 202. As best shown in FIG. 4, cover 218 is secured to extension member 216 and is movable therewith for maintaining the longitudinally extending slot 220 closed to prevent the entrance of dirt or other contaminants.
Extension member 216 carries second blank holding member 222 which engages the blank 194 in coaxial alignment with first blank holding member 190. The blank holding member 222 permits the blank 194 to rotate on its central axis in response to rotation of shaft 184. Those skilled in the art will appreciate that the displacement of rod 208 will cause second blank holding member 222 to approach or move away from blank 194 so as to cause the blank 194 to be clamped between the blank holding members 190 and 222 or to be released therefrom. Preferably, the pad 192 includes an adhesive for securing the blank 194 to block 191. It is also preferred that the blank holding member 190 be readily removable and replacable on the shaft 188 so as to maximize the operation of the shaper P.
As best shown in FIG. 3, shaft 186 has cam 224 mounted thereto for coaxial rotation therewith. Switch 226 is mounted adjacent cam 224 and has a contact member 228 engaged with the cam 224 for determining the proper angular position of shaft 186.
First pattern holding member 230 is mounted to cam 224 for coaxial rotation therewith. Preferably, first pattern holding member 230 has pins 232 and 234 which are positioned in cooperating apertures in pattern 236. The pins 232 and 234 thereby prevent rotation of the pattern 236 relative to the first pattern holding member 230. Therefore the pattern 236 does not come out of position and cause the blank 194 to be cut to other than the prescribed shape. Similarly, because of switch 226, the pattern always is positioned in the same horizontal relation when operation is commenced.
Supports 238 and 240 are secured to second frame 156 in spaced parallel relation and extend parallel to support members 196 and 198. Rods 242 and 244 extend between supports 238 and 240. It can be noted in FIG. 7 that the rod 244 is a slight distance above the second frame 156 relative to the rod 242. Arm 246 is mounted to the rods 242 and 244 for movement therealong between the support members 238 and 240. Arm 246 has second pattern holding member 248 mounted to the distal end thereof. Second pattern holding member 248 rotates on an axis coaxial with shaft 186. Second pattern holding member 248 has contact member 250 which engages pattern 236.
Pneumatic cylinder 252 is secured to support member 238 by lock nut 254. The piston rod 256 thereof is secured to arm 246 and causes the arm 246 to be moved on the rods 242 and 244. Those skilled in the art will appreciate that displacement of the rod 256 will cause corresponding movement of the arm 246 such that the pattern 236 will be clamped or released from between the pattern holding members 230 and 248.
As best shown in FIGS. 3 and 7-8, third frame 258 is secured to bed 60 through support 259 and extends upwardly therefrom. Front frame member 260 is similarly secured to support 259 and extends upwardly therefrom in spaced parallel relation relative to third frame 258. Third frame 258 includes threaded aperture 262 in which threaded rod member 264 is rotatably mounted. Threaded member 264 includes a shaft 266 extending therefrom and having a handle 267, as best shown in FIG. 1, exterior of bottom member 10. Preferably, handle 267 has gradients 268 equiangularly marked thereabout. Locator 270 has slot 271 aligned with the gradients 268. Rotation of handle 267 and alignment with of one of the gradients 268 by slot 271 causes the threaded member 264 to move inwardly and outwardly relative to the third frame 258.
Sliding member 272 extends between third frame 258 and front frame member 260 and carries pattern engaging roller 274 which rotates on an axis parallel to the axis of rotation of shafts 184 and 186 and 104. As shown in FIGS. 3 and 7, arms 276 and 278 extend outwardly from sliding member 272 and the roller 274 extends rotatably therebetween. Contact plate 280, as best shown in FIGS. 7 and 8, is engaged with threaded member 264 so that movement of member 264 towards the pattern 236 causes associated displacement of the sliding member 272, and thereby of pattern engaging roller 274. In this way, the pattern engaging roller 274 may be moved inwardly relative to the pattern 236 so that adjustments in the size of the cut blank 194 may be accomplished with precision through the micrometer assembly provided by the gradients 268 and the locator 270. The pattern engaging roller 274 is moved outwardly because of pressure from second frame 156 and the movement outwardly of member 264.
Cam assembly 282 is mounted for rotation on sliding member 272 by means of a cam motor 284. Cam assembly 282 includes first cam portion 286 and second cam portion 288. Cam operated switches 290 and 292 have cam engaging members 296 and 294, respectively, each of which is engageable with one of the cam portions 288 and 286, respectively. In this way, rotation of the cam assembly 282 and causes corresponding rotation of the cam portions 286 and 288 and thereby operation of the switches 190 and 292. The switches 290 and 292 are in electrical connection with the control mechanism, as will be further explained, and cause the first frame 78 to be shifted on its axis.
As best shown in FIGS. 3 and 9, arm 298 extends from bracket 116 and carries support 300 at the distal end thereof and the height of support 300 can be adjusted through knob 132. Shaft 302 is mounted for rotation to support 300 and has wheel 304 at the distal end thereof. As can be seen in FIGS. 3 and 9, wheel 304 has an angled periphery 306 which is engaged with the blank 194 during the cutting operation thereof. In this way, the periphery 306 engages blank 194. It can be noted in FIG. 9 that the periphery 306 is radially inwardly spaced from the V-shaped beveled edge of the blank 194.
FIG. 4 discloses support block 308 to which solenoid assemblies 310 are mounted. Those skilled in the art will understand that a solenoid 310 is required for causing operation of the cylinder and piston assemblies hereof in order to effectuate movement of the frames 78 and 156, as well as of the arm 214. While only one solenoid assembly is illustrated in FIG. 4, those skilled in the art can appreciate that that appropriate number is provided.
FIG. 10 illustrates the wiring schematic which controls the operation of plastic lens finisher and shaper P. The cutter motor is connected to a mercury switch affixed to the underside of cover member 12 so that the motor will not operate when the cover member 12 is raised. Similarly, the vacuum which evacuates air and dust through shroud 142 is in circuit connection with the cutter motor, as is the cam motor and the speed control device for the motor 180 which rotates the pattern and the lens blank.
FIG. 10 also illustrates the on/off push button, as well as the chuck push button, the start push button which initiates operation of the device, the cycle halt push button, the rimless push button and the emergency stop push button. These push buttons correspond with the push buttons 30, 32, 34, 36, 38 and 40 and have for their purpose the selective operation of the shaper and finisher P. The start push button is in circuit connection with the mercury switch 22 to prevent the motor 102 from being operated when the window 16 is in the up position. Also in circuit connection with the start push button is a counter assembly so that the operator will know how many lens blanks 194 have been cut. The solenoid assemblies 310 are also in circuit connection with the push buttons and it can be noted that three solenoid assemblies are provided. Also in circuit connection with the start button is a relay which permits operation of the device.
Yet another mercury switch is affixed to the underside of window 16 and is a safety feature which prevents the cam motor 284 from being started unless cover 12 is lowered and the chuck push button depressed.
A cycle switch is also provided for keeping the cycle going once initiated. A shift switch is provided which operates in conjunction with the cam assembly 282 for shifting the first frame 78 to the right so that the V-portion 114 is engaged with the periphery of the blank 194 after the initial shaping has occurred. A drive switch is also provided for keeping the motor 180 operating so that the pattern 236 is always in a preselected, preferably horizontal position, when the start push button is initiated.
0 P E R a T I 0 N
The plastic lens shaper and finisher P is relatively simple to operate because of the pneumatic cylinder and piston assemblies which drive the first frame 78 and the second frame 156 and which operate the pattern clamping mechanism and the lens blank clamping mechanism.
Initially, the connection 48 must be made with a source of pressurized air and, naturally, power provided through plug connections 50 and 52. The on/off push button is then depressed to power the system and to operate the light 20 under the window 16. The handle 120 is then slid to the right by movement of frame 78 at the end of the previous cycle, as viewed in FIG. 1, and the window 16 may then be raised because the rod 134 will have been removed from the aperture 138 in the latch 136. The appropriate pattern 236 is then mounted to the pins 232 and 234 of first pattern holding member 230. A lens blank 184, having affixed thereto pad 192 and block 191 is indexed with first pattern holding member 190.
The chuck push button is depressed which thereby causes the arm 246 to be displaced so that the contact member 250 engages the pattern 236 and clamps the pattern 236 between the first and second pattern holding members 230 and 248, respectively. Simultaneously, the piston rod 208 likewise shifts and thereby causes the second blank holding member 222 to engage the blank 194 and thereby secure the blank 194 between the first and second pattern holding members 190 and 222. The window 16 may then be lowered.
At this time, or even earlier, the handle 267 is rotated to cause the appropriate gradient 267 to be aligned in the notch 271 of the locator 270 so that the proper size is selected. As previously explained, rotation of the handle 267 causes cooperating inward movement of the sliding member 272 so that the pattern engaging roller 274 is moved inwardly. Naturally, rotation of handle 267 in the opposite direction will permit sliding member 272 to slide in the opposite direction.
Assuming that a beveled edge is desired for the finished blank 194, then the start push button is depressed which shifts frame 78 to the left and thereby secures rod 134 in latch 136. This causes the counter to signal one cycle and also initiates the solenoids which drive the first and second frames 78 and 156, respectively. Shifting of first frame 78 to the left, as viewed in FIG. 3, aligns the straight portion 112 of the blades 110 with the periphery of the blank 194. As noted in FIG. 3, this also causes the periphery 306 of the wheel 304 to engage the side surface of the blank 194.
Simultaneously, the piston 176 is displaced, as is the piston 168 which causes movement of the frame 156 along the travel axis. The piston 176 continues to be displaced and thereby permits the piston 168 to continue to displace the frame 156 toward the router 106. Eventually, displacement of the piston 168 causes the pattern 236 to engage the pattern roller 274, such that the cylinder 174 need no longer function as a damper. At this point, the piston 168 of the cylinder 166 is responsible for exerting the necessary application pressure so that the pattern 236 stays in engagement with the pattern engaging roller 274, which necessarily causes the blank 194 to be cut by the router 106.
Those skilled in the art will appreciate, and as illustrated in FIG. 7, that the pattern 236 is of non-uniform contour such that the periphery thereof is not a constant distance from the central rotational axis thereof. The overall effect is that engagement of the pattern 236 with the roller 274 causes the frame 156 to be shifted toward and away from the router 106 as dictated by the contour of the pattern 236. The relatively small cylinder 166 is not pressurized by an amount which would prevent the piston 168 from being displaced inwardly toward the cylinder 166 when forced in that direction by the contour of the pattern 236. The net result is that the piston rod 168 moves in response to the contour of the pattern 236 but maintains essentially uniform pressure so that constant cutting pressure is maintained between the periphery of the blank 194 and the router 106. Damping by cylinder 174 is not needed after engagement because the pattern 236 typically does not change its contour by an amount which cannot be accommodated by movement of piston 168.
While this preferred embodiment is described with reference to a physical pattern 236, those skilled in the art will appreciate that modern computer techniques are sufficient to permit digitization of a pattern. Digitization would avoid the necessity of the physical pattern, as well as the cam and cam switches related thereto.
The cam assembly 282 rotates in cooperation with rotation of the pattern 236 and the blank 194. After the blank 194 has completed slightly in excess of one rotation, as noted by the cam 286 and the cam switch 292, then the first frame 78 is shifted to the right so that the V-shaped beveled portion 114 is aligned with the blank 194. Again, substantially one revolution of the blank 194 is made, as indicated by the cam 288 and the cam switch 290, and the blank is then appropriately shaped and edged. The cycle stops automatically and the operator may depress the chuck push button so as to permit removal of the finished blank 194 after switch 226 indicates proper horizontal positioning of the pattern 236.
Should the blank 194 not require a beveled edge, then the operator can merely depress the rimless push button. This has the effect of completing the shaping and finishing operation by avoiding the shifting of the first frame 78 to the right.
Should the operator desire to halt the cycle at some point, for whatever reason, then he need merely depress the cycle halt push button. This has the effect of stopping motor 284 causing the shaper and finisher P to remain at that point in the cycle until the cycle halt push button is depressed again.
The switch 226 engaged with cam 224 assures that the pattern 236 is always in the same initial starting position when the device is operated because the cycle terminates when the pattern 236 reaches this position.
Should the pattern need to be changed, because a different type lens is to be cut, for example, then the operator need merely depress the chuck push button in order to access the pattern 236 and permit its changing. The disclosed invention also makes it possible to cut a pattern from a previously finished lens. This is because the cutting pressure exerted by the piston 168 is so relatively slight that the pattern material will not become distorted. Heretofore, it has been necessary for the operator to have a pattern, as determined by the manufacturer, or else no lens could be cut unless the operator had a pattern maker. Now, because the right and left lens are mirror images of each other, a pattern can be made from one lens to permit the cutting and finishing of the other other.
While this invention has been described as having a preferred design, it is understood that it is capable of further modifications, uses and/or adaptations of the invention following in general the principle of the invention and including such departures from the present disclosure has come within known or customary practice in the art to which the invention pertains, and as may be applied to the central features hereinbefore set forth, and fall within the scope of the invention of the limits of the appended claims.